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Learn SQL

A free, interactive online SQL course. You run real SQL queries against live tables on every lesson, with AI hints when a query doesn't return what you expect, and a free certificate when you finish.

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View syllabusSQL playground

141,120+ codders enrolled

99 lessons94 challenges527 quiz questions

  • Beginner friendly
  • sparkles iconAI-assisted coding help
  • hint iconHands-on interactive lessons
  • volume On iconAudio narration on every lesson
  • quiz iconQuizzes to test your knowledge
  • certificate iconFree certificate of completion

Syllabus

2 sections1 projects99 lessons94 challenges527 quiz questions
  1. Section 1

    Fundamentals

    Start sectionStartExpandCollapse    Learn how to create databases, define tables, and perform simple queries.72 lessons72 challenges360 questions1 project

    Introduction

    4 lessons423

    Conditions

    7 lessons1256

    Specific Return Format

    6 lessons630

    More Keywords

    5 lessons532

    Arithmetic Operations

    4 lessons332

    Intro Challenges

    4 lessons4

    Dates

    3 lessons325

    Statistics

    9 lessons950

    Multiple tables

    9 lessons944

    Imaginary Products

    Project5 lessons1

    Window Functions part 1

    8 lessons836

    Window Functions part 2

    5 lessons532

    Summary

    3 lessons3
  2. Section 2

    Beyond the Basics

    Start sectionStartExpandCollapse    Practical SQL on top of the fundamentals: conditional logic, string functions, pivoting with conditional aggregation, set operations, recursive CTEs, modifying data, and analytics recipes.27 lessons27 challenges167 questions

    Conditional Logic

    5 lessons532

    String Functions

    6 lessons640

    Conditional Aggregation

    4 lessons424

    Set Operations

    4 lessons423

    Recursive CTEs

    3 lessons316

    Analytics Recipes

    5 lessons532

SQL courses

Hands-on SQL courses, free to start in your browser.

SQL Challenges pack #1

In this course you will challenge yourself with SQL problems.

  • 3
  • 1

SQL Challenges pack #2

In this course you will challenge yourself with SQL problems.

  • 3
  • 1
What you get
Everything you'll use to learn to code

Learn by Doing

Write real code, query databases, build websites, and master AI prompts. Our interactive lessons cover every skill modern developers need.

playground.js
Code Editor
1const greeting = "Hello, Coddy!"
2function sayHi(name) {
3    return greeting + " " + name
4}
5
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Test #3test Case Failure icon
Input
"Alex"
Output
"Hello, Coddy! Alex"

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January 2026

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Take your coding journey on the go! No setup, no downloads - just open and start coding. Available on iOS, Android and Web with 4.9 star ratings.

Python
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Variables
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CONTINUE
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Compete on global leaderboards, invite friends to earn rewards, and celebrate each other's wins. Coding is better with friends!

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Every way to learn

Read, listen, test yourself, ask the AI, or look up anything you've already covered. Every lesson meets you where you are.

Intro to Variables
Audio

A variable is a named container that stores a value you can reference later in your program.

In Python, you create one by writing the name, an equals sign, then the value you want to store.

The value can change over time - reassigning the name simply points it to a new value.

1xSarah

Prove Your Skills

Earn certificates for every course you complete. Add them to your LinkedIn profile and resume to showcase your coding expertise to employers.

CoddyCertificate of Completion
This certifies thatJohn Doehas successfully completed
PythonPython Fundamentals
Verified
DateJan 2026
LinkedInAdd to LinkedIn

Why learn SQL with Coddy

  • Run real SQL online. Every lesson runs against a live SQLite database in your browser, so you write actual SELECT, JOIN, and GROUP BY queries, not pseudo-code.
  • SQL basics through advanced patterns in one course: filtering, sorting, multi-table joins, aggregations, subqueries, window functions. The SQL you actually need at work.
  • AI hints walk you through query mistakes - wrong joins, missing GROUP BY columns, off-by-one filters - without just handing you the answer.
  • Free SQL certificate when you finish, plus the option to keep practicing with quizzes and projects so the SQL skills don't fade after the course.

Frequently asked questions about learning SQL

Is SQL hard to learn?

SQL is one of the easier languages to pick up because it's declarative - you describe what you want, not how to compute it. The basics (SELECT, WHERE, ORDER BY) take a few hours. Joins, subqueries, and window functions are where most of the depth lives, and the course introduces them in small, queryable steps.

How long does it take to learn SQL?

You can learn SQL basics in a week of daily practice. Comfortable use of joins, aggregations, and subqueries usually takes two to four weeks. Reaching expert level - query optimization, window functions, CTEs - takes longer and is mostly driven by working on real data.

Where can I practice SQL online for free?

Coddy is a free SQL learning platform. Every lesson includes an in-browser SQL editor with real seed tables, so you write and run SQL queries against actual data without setting up a database locally.

Do I need to install a database to learn SQL here?

No. Every SQL exercise runs in your browser against a sandboxed SQLite database with realistic seed tables. You don't need to install Postgres, MySQL, or any other database engine to learn SQL.

Which SQL dialect does this course teach?

The course is dialect-agnostic for the fundamentals and uses SQLite under the hood. Standard SQL - SELECT, joins, aggregations, subqueries, CASE, GROUP BY - works the same in Postgres, MySQL, SQL Server, and Snowflake. Dialect-specific features are called out where relevant.

Do I get a certificate after the SQL course?

Yes. Finishing the SQL course gives you a free certificate of completion you can add to your resume or share on LinkedIn - useful for analyst, data engineer, and back-end roles where SQL is a baseline expectation.
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Learn SQL with Coddy

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